The invention relates to a method for determining the position of a medical instrument introduced into an object to be examined and for imaging the vicinity of the medical instrument. The invention also relates to a corresponding device as well as to a corresponding medical instrument and to a computer program.
U.S. Pat. No. 5,638,819 discloses a method via which a medical instrument, notably a biopsy needle or an endoscope, can be introduced into a patient along a desired trajectory, notably into the brain of a patient. For the localization of the instrument a sensor is arranged at the end of the instrument which is not introduced into the patient; the position of this sensor relative to a reference co-ordinate system can be determined by means of an appropriate measuring device. For the navigation of the instrument the position thereof is reproduced in a two-dimensional tomographic image while a live video image of the endoscope is displayed at the same time. However, the known method is suitable only for the localization and navigation of rigid medical instruments, because it is only in the case of a rigid instrument that reliable information concerning the position of the part of the instrument that is present within the patient can be derived from the position of the sensor arranged on the part of the instrument that is situated outside the patient.
Therefore, it is an object of the present invention to provide a method and a device which enable localization and navigation of any medical instrument introduced into an object to be examined.
In accordance with the invention this object is achieved by means of a method wherein the position of the medical instrument within the object to be examined is determined by means of a localization device that is arranged in the end zone of the medical instrument that is to be introduced, image information concerning the vicinity of the medical instrument being acquired at the same time by means of an image acquisition device arranged on the medical instrument, the position of the medical instrument being reproduced in a survey image of the object to be examined on the basis of the position determined, and images of the vicinity of the object to be examined which are associated each time with the relevant position being displayed on the basis of the image information acquired.
This object is also achieved by means of a device which includes
localization means for determining the position of the medical instrument in the object to be examined, a localization device being arranged in the end zone of the medical instrument that is to be introduced,
imaging means for the acquisition at the same time of image information concerning the vicinity of the medical instrument, an image acquisition device being arranged on the medical instrument, and
data processing and display means for determining and displaying the position of the medical instrument in a survey image of the object to be examined, that is, on the basis of the position thus determined, and for determining and displaying images of the vicinity of the object to be examined, said images being associated with the relevant position, on the basis of the image information acquired.
The invention is based on the idea that, as opposed to the known method, notably in the case of flexible medical instruments, for example catheters which are used above all for intravascular interventions, it is not possible to arrange a localization device for determining the medical instrument on the part of the instrument that is not introduced into the object to be examined. This is because in that case the mounting of optical sensors or markers on the end of a catheter which projects from the object to be examined and the determination of the position of these sensors or markers, for example by means of an optical position measuring system, would not provide reliable information as regards the position of the tip of the catheter or the course of the catheter introduced into the object to be examined. Therefore, in accordance with the invention the localization device is arranged in the zone of the medical instrument which is also introduced into the object to be examined, notably in the inserted end zone of the medical instrument, because particularly the position thereof during the intervention is of interest. In order to acquire also image information from this zone at the same time, in accordance with the invention it is also proposed to arrange in said zone an image acquisition device which serves to acquire image information concerning the vicinity of the introduced medical instrument simultaneously with the determination of the position thereof. The image information and the position information thus acquired is used in accordance with the invention to display the instantaneous position of the medical instrument each time in a survey image of the examination zone, for example in an angiogram or in a so-called Road Map in the case of an intravascular intervention, and to display at the same time one or more instantaneous images of the vicinity of the medical instrument.
In accordance with an advantageous version the survey image may be formed from a three-dimensional or four-dimensional image data set, the four-dimensional image data set having a temporal resolution in addition to the spatial resolution. This means that different image data sets are obtained at different instants, for example, during the cardiac motion phase; in such different image data sets above all different positions of the anatomy examined at the various instants are taken into account or corrected. The image data sets themselves may have been acquired by means of an arbitrary imaging method, for example, by means of magnetic resonance tomography, computed tomography, an X-ray method, notably a three-dimensional rotation X-ray method, or by means of an ultrasound method.
Furthermore, the survey image may be advantageously formed from a motion-compensated image data set for which notably the cardiac motion and/or the respiratory motion is compensated; such motions have different effects on the anatomy in dependence on the region examined. Appropriate methods are known for such compensation. For example, for the compensation of the cardiac motion it is possible to form an electrocardiogram during the acquisition of the image data in order to associate the image data with a respective given cardiac phase and to correct the effects of the cardiac motion on the anatomy in the individual cardiac motion phases on the basis of a cardiac model. For the correction of the respiratory motion there are appropriate models and sensors that monitor the respiratory motion and determine and compensate the effects thereof on the anatomy.
Various advantageous embodiments of the localization device used. This device may be a magnetic field sensor whose position is determined by means of an external measuring device, or an active or a passive microcoil whose position can be determined by means of a magnetic resonance device, or also an ultrasound sensor which can be detected by means of an ultrasound device. Moreover, the medical instrument may also consist at least partly of a material that can be detected by means of an ultrasound device or a magnetic resonance device. Also feasible is any other punctiform signal source that can be arranged on the medical instrument and whose signal can be detected by an external detector device so as to determine the position of the signal source therefrom.
Advantageous further possibilities for the use of an image acquisition device are provided. That is, it is a common aspect of all image acquisition devices that they are preferably arranged in the end zone of the medical instrument that is to be introduced, because notably image information from this region is of interest. The transfer of the acquired image data may take place in a contactless manner or via leads. Many further embodiments of the image acquisition device additionally require external image acquisition means for the acquisition of image information. For example, one embodiment of the MR device which is preferably implemented as a microcoil requires an external excitation coil as it is used in a magnetic resonance tomography device. Other further embodiments, for example an internal excitation and measuring coil, an endoscope or an intravascular ultrasound device, however, do not require additional external image acquisition means.
For the navigation and continuous monitoring of the position of the medical instrument during an intervention, the localization and imaging are preferably performed continuously or at regular intervals, the instantaneous position and the associated images being displayed each time.
It is particularly advantageous to use the invention for the navigation in blood vessels such as, for example the coronary vessels, during an intravascular intervention. The invention, however, can also be used for navigation in other cavities of an object to be examined, for example in the intestine or the esophagus of a patient.
The invention is used particularly advantageously in conjunction with flexible medical instruments such as, for example catheters as used notably also for the examination and treatment of coronary vessels. The invention provides the physician with instantaneous information concerning the position of the catheter as well as with image information from the end zone of the catheter during the travel of the catheter inside the patient, thus enabling very precise navigation in reaching the target area.
The invention also relates to a corresponding device for determining the position of a medical instrument in an object. The invention furthermore relates to a medical instrument to be introduced into an object to be examined, which instrument includes a localization device that is arranged in the end zone that is to be introduced and serves to determine the position of the medical instrument in the object to be examined, and also includes an image acquisition device for the simultaneous acquisition of image information concerning the vicinity of the medical instrument, the position determined being intended for use in determining and reproducing the position of the medical instrument in a survey image of the object to be examined and the acquired image information is intended to form and reproduce images of the vicinity of the object to be examined which is associated with the relevant instantaneous position. The device as well as the medical instrument may be elaborated in accordance with the invention so as to form advantageous embodiments which are identical or analogous to the versions disclosed above for the method.
The invention also relates to a computer program with program sections for executing the method in accordance with the invention and/or for controlling the device in accordance with the invention or the medical instrument in accordance with the invention during execution of the computer program by a computer.